ASTM D3913-2003 Standard Test Method for Acidity in Basic Chromium Tanning Liquors《碱性铬鞣革液中酸度的标准试验方法》.pdf

1、Designation: D 3913 03Standard Test Method forAcidity in Basic Chromium Tanning Liquors1This standard is issued under the fixed designation D 3913; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number

2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the titrat-able acidity of chromium tanning liquors. By titratable acidityis meant not only fre

3、e acidity, which is rarely present, but alsoanions combined with weakly basic cations such as Chromium(III), which can be titrated with base at the phenolphthalein endpoint.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili

4、ty of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 3898 Test Method for Chromic Oxide in Basic Chro-mium Tanning Liquors2E 180 Practice for Determini

5、ng the Precision of ASTMMethods for the Analysis and Testing of Industrial Chemi-cals33. Summary of Test Method3.1 A sample of suitable size is taken by diluting andaliquoting, if necessary. The sample is then heated to boilingand titrated hot to the first appearance of a pink color, stable toboilin

6、g in the supernatant solution, as determined by viewingthe settled solution against the rim of a porcelain dish, oragainst the light in a tall beaker or Erlenmeyer flask.4. Significance and Use4.1 The acidity of a chrome tanning liquor, as determined bythis test method, is rarely employed as such. T

7、his result isnormally combined with the results of a chromium analysis(see Test Method D 3898) to determine a property of the liquorcalled basicity. This property, equal to the percentage by whichanions in a normal chromic salt have been replaced byhydroxyl in the solution being analyzed, is closely

8、 related tothe tanning behavior of the solution.5. Interferences5.1 Although for most purposes, the results of this analysisare intended to give a measure of the acid anions associatedwith chromium, it should be mentioned that any weak basiccation will behave similarly. Hence, aluminum, zirconium,fe

9、rric iron, and weak organic bases will all yield salts withacidity titratable by this test method. A discussion of the effectof these interferences has been published.45.2 If there are anions which form very stable complexeswith chromium present in the solution, the titration:CrOHxXyH2O!62x2y!x1y23!

10、21 3 2 x!OH2CrOH!31 yX21 62x2y!H2O (1)where:X = stable complexes,will not go to completion at the phenolphthalein endpoint andthe acidity reported will be low. Large excess of oxalate orcomplexing anions of lesser affinity used for masking effectwill introduce this error.5To obviate this, an entirel

11、y differentmethod has been developed in which the hydroxyl groups aretitrated and the chromium is completely complexed by oxalate.This is generally referred to as the Lehigh method and may beused if complex ions are present in interfering amount.6,76. Reagents and Materials6.1 Purity of ReagentsReag

12、ent grade chemicals shall beused in all tests. Unless otherwise specified, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.8Other grades may be1This test method is un

13、der the jurisdiction of ASTM Committee D-31 on Leatherand is the direct responsibility of Subcommittee D31.06 on Chemical Analysis-General Methods. This test method was developed in cooperation with the AmericanLeather Chemists Assoc.Current edition approved May 10, 2003. Published July 2003. Origin

14、allyapproved in 1991. Last previous edition approved in 1993 as D 3913 93 (1998).2Annual Book of ASTM Standards, Vol 15.04.3Annual Book of ASTM Standards, Vol 15.05.4Hartford, W. H., JALCA, Vol 56, 1961, p. 568.5Thorstensen, T. C., and Theis, E. R., JALCA, Vol 47, 1952, p. 583.6Theis, E. R., and Tho

15、rstensen , T. C., Journal International Society LeatherTrade Chemists, Vol 31, 1947, p. 124.7Serfass, E. J., Theis, E. R., and Clark, A., Jr., The Journal of the LeatherChemists Association, Vol 42, 1947, p. 360.8Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society,

16、Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copy

17、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.used, provided it is first ascertained that the reagent is ofsufficient high purity to permit its use without lessening theaccuracy of the determination.6.2 Purity of WaterUnless otherwise s

18、pecified, referenceto water shall be understood to mean distilled water or water ofequal purity.6.3 Sodium Hydroxide, 0.1 NDissolve 42 g NaOH inabout 60 mL water. Cool and transfer to a 100-mL volumetricflask; dilute to the mark, stopper, mix, and allow any turbidityto settle. Pipet 10 mL of the cle

19、ar solution to a 1-L volumetricflask; dilute to mark and mix well. Keep stoppered andprotected from atmospheric carbon dioxide.6.3.1 StandardizationDry potassium hydrogen phthalate,KHC8H4O4, in an oven for2hat120C and cool in desiccator.Weigh about 0.8 g to an accuracy of 0.1 mg into a 400-mL tallbe

20、aker or Erlenmeyer flask. Dissolve in 200 to 250-mL waterand titrate with the sodium hydroxide to be standardized, usingphenolphthalein indicator.normality of sodium hydroxide 5weight K phthalate0.20423 3 mL titration(2)6.4 Phenolphthalein Indicator, 5 %Dissolve 5 g phenol-phthalein in 100 mL 95 % e

21、thanol.7. Procedure7.1 The results are more meaningful if the same sampleused for the chromium determination is used for the aciditydetermination; for example, a specimen that consists of aweighed quantity of the liquor diluted to a definite volumecontaining from 0.003 to 0.004 g of chromic oxide pe

22、rmillilitre. Transfer 25-mL aliquots for testing.7.2 Two procedures have been found about equally effectivefor determining the endpoint. The results differ slightly, asshown in the section on precision and bias. Hence, the resultsby the two procedures cannot be compared exactly.7.3 Procedure 1Transf

23、er the 25-mL aliquot to a 7-in.porcelain casserole. Add 400 mL water and 1 mL 5 %phenolphthalein. Boil and titrate while boiling with standard-ized 0.1 N sodium hydroxide until a faint pink color, as seen atthe side of the casserole after settling, persists for one minute.7.4 Procedure 2Transfer the

24、 25-mL aliquot into a 400-mLtall beaker. Dilute to 250 mL. Heat to boiling, remove from theheat, add 10 drops 5 % phenolphthalein and titrate until a pinkcolor is barely noted. Boil again for ten minutes and retitrateuntil a faint pink color is barely noted on settling. Boil a thirdtime and complete

25、 the titration. (The process may be expeditedby using two, preferably three, aliquots of the sample, in whichone is titrated according to the above procedure, and the othershave 0.5 mL increments of additional 0.1 N NaOH added.Interpolate the end point after the second boiling.8. Calculation8.1 Calc

26、ulate acidity in milliequivalents per millilitre oforiginal sample as follows:Acidity, me/mL 5A 3 NW3V25(3)where:A = the number of mL of standard sodium hydroxiderequired to titrate the 25 mL aliquot of the specimen,N = the normality of the sodium hydroxide solution,W = the weight of the specimen be

27、fore dilution, g, andV = the volume to which W was diluted, mL.NOTE 1The acidity in me/mL is numerically equal to equivalents/litreor normality.8.2 Unless otherwise specified, test two 25 mL aliquotsfrom the diluted specimen.8.3 The acidity in the sample for the test shall be the averageof the test

28、results obtained from the two aliquots tested.8.4 Record the acidity to the nearest 0.1 %.9. Precision and Bias9.1 The precision of this test method, as determined byanalysis of variance on a round robin test using triplicatedeterminations on four samples in three laboratories gave thefollowing devi

29、ations, expressed as a percentage of the aciditypresent:Procedure I Procedure IIRepeatability (within laboratories) 0.48 0.72Reproducibility (between laboratories) 1.84 2.789.2 Although an attempt was made to refer the results of thistest to knowns and so determine accuracy, the analysis ofvariance

30、shows a significant variability attributable to samplemakeup (variations in acidity, formate, and sugar content). Thisamounts to an estimated standard deviation, 2.6 and 2.86 % byProcedure I and Procedure II, respectively. The overall averagebias for all samples is 0.46 % for Procedure I and 0.94 %

31、forProcedure II.10. Keywords10.1 acidity; basic chromium tanning liquor; basicityASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the va

32、lidity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your co

33、mments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments hav

34、e not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D3913032